April, 2026
Plagiocephaly vs Brachycephaly
Plagiocephaly is one-sided head flattening, while brachycephaly is symmetrical flattening across the back of the head.
These positioning-related head shape changes are common between 2 and 6 months of age, when a baby’s skull is soft and growing quickly.
The American Academy of Pediatrics and institutions such as Cleveland Clinic recognize positional head shape changes as common in early infancy. This does not automatically mean there is a problem with brain growth, as these conditions usually affect outer skull shape rather than brain development.
What plagiocephaly looks like
Plagiocephaly affects one side of the back of the head more than the other. From above, the head may appear uneven, and one ear may look slightly more forward. The shape is sometimes described as a parallelogram when viewed from the top.
The defining feature is measurable asymmetry.
What brachycephaly looks like
Brachycephaly affects both sides of the back of the head evenly. The head may look wider from side to side and shorter from front to back. From above, the flattening appears symmetrical rather than diagonal.
The defining feature is increased width relative to length.
Why these head shapes develop
Both conditions usually develop because babies spend long periods lying on their backs during the first months of life. A baby’s skull expands rapidly in early infancy, and growth follows the path of least resistance.
When pressure is repeated on one area, the soft skull gradually adapts to that shape over time.
How clinicians measure plagiocephaly
Clinicians measure plagiocephaly using the Cranial Vault Asymmetry Index, or CVAI. This compares diagonal skull measurements to calculate percentage asymmetry. The goal is objective assessment rather than visual impression alone.
CVAI helps track whether asymmetry is improving over time.
How clinicians measure brachycephaly
Brachycephaly is measured using the Cephalic Index, or CI, which compares head width to head length. A higher ratio means the head is proportionally wider.
CI helps determine whether proportions fall within expected age ranges and whether change is occurring over time.
What not to assume or do
Plagiocephaly and brachycephaly are usually cosmetic positioning conditions and do not affect intelligence or brain growth. These patterns are different from craniosynostosis, where a skull suture closes too early.
Do not use sleep positioners, wedges, or side-sleeping to try to correct head shape when the baby is asleep, as safe sleep guidance recommends placing babies on their backs on a firm, flat surface.
If you are unsure which head shape pattern you are seeing, a structured head shape scan can provide objective clarity instead of relying on visual comparison alone.
When to seek advice
Plagiocephaly and brachycephaly are usually cosmetic positioning conditions and do not affect intelligence or brain growth. These patterns are different from craniosynostosis, where a skull suture closes too early.
Do not use sleep positioners, wedges, or side-sleeping to try to correct head shape when the baby is asleep, as safe sleep guidance recommends placing babies on their backs on a firm, flat surface.
If you are unsure which head shape pattern you are seeing, a structured head shape scan can provide objective clarity instead of relying on visual comparison alone.
When helmet therapy may be discussed
Helmet therapy may be discussed when age, CVAI, or CI measurements remain elevated despite repositioning efforts. Decisions are based on combined factors including age, growth rate, and measurement trend. Many mild cases improve naturally as babies roll, sit, and spend less time resting on the same area.
If you would like objective insight into your baby’s head shape pattern, structured measurement can support calm and informed next steps.
Common questions parents ask
Is plagiocephaly worse than brachycephaly?
They are different patterns and are evaluated using different measurements.
Does plagiocephaly correct itself?
Mild cases often improve as babies gain mobility.
Can brachycephaly affect brain development?
It is usually cosmetic and does not impair brain growth.
When does head flattening peak?
It is most noticeable between 2 and 6 months of age.
Is helmet therapy always needed?
No, most babies improve with positioning and natural growth.
Writen by Elly van der Grift
Elly van der Grift is the co-founder of Skully Care and a pediatric physiotherapist with over 30 years of experience. Her mission is to provide top care for babies with skull deformities. With her infectious enthusiasm, she shares simple, effective tips that can make a big difference for your baby. Working with Elly, you'll feel confident and supported in your baby’s journey to better health.